In deciding how best to meet the world's growing needs for energy, the answers depend crucially on how the question is framed. Looking for the most cost-effective path provides one set of answers; including the need to curtail greenhouse-gas emissions gives a different picture. Adding the need to address looming shortages of fresh water, it turns out, leads to a very different set of choices.
That's one conclusion of a new study led by Mort Webster, an associate professor of engineering systems at MIT, published in the journal Nature Climate Change. The study, he says, makes clear that it is crucial to examine these needs together before making decisions about investments in new energy infrastructure, where choices made today could continue to affect the water and energy landscape for decades to come.
The intersection of these issues is particularly critical because of the strong contribution of the electricity-generation industry to overall greenhouse-gas emissions, and the strong dependence of most present-day generating systems on abundant supplies of water. Furthermore, while power plants are a strong contributor to climate change, one expected result of that climate change is a significant change of rainfall patterns, likely leading to regional droughts and water shortages.
Surprisingly, Webster says, this nexus is a virtually unexplored area of research. "When we started this work," he says, "we assumed that the basic work had been done, and we were going to do something more sophisticated. But then we realized nobody had done the simple, dumb thing"—that is, looking at the fundamental question of whether assessing the three issues in tandem would produce the same set of decisions as looking at them in isolation.
The answer, they found, was a resounding no. "Would you build the same things, the same mix of technologies, to get low carbon emissions and to get low water use?" Webster asks. "No, you wouldn't."